There are a host of different braking arrangements for vehicles which have been proposed, with the most popular braking system being either the Drum Brake or more recently the Disk Brake. In addition to these two types of braking systems there is also what is referred to as a Ring Brake, as generally shown in U.S. Pat. No. 3,170,542, where braking can occur on both sides of the ring brake member.
Common to all of these braking systems is the dissipation of energy by means of heat which is generated at or on the braking surface. This heat is dissipated to the surrounding air environment by means of convection, however, due to the placement of the brake, generally in a confined region under a vehicle, the circulation of air is relatively poor and the convection coefficient of heat transfer is relatively low. This problem of heat build-up is particularly acute where the brake must be operated frequently over a long period of time and thus, the braking system does not have an opportunity to dissipate the heat when the brake is not in use. Such circumstances-commonly occur with truck braking systems, particularly in mountainess regions, and the possibility of brake failure is quite acute. For example, there are often run-off regions where vehicles that are out of control (i.e. where braking system is substantially lost) may exit into these regions which are designed to stop the vehicle.
Most conventional car braking systems operate satisfactorily, however, braking systems used to maximum, say eight times in a row, often result in the effective braking power being reduced to less than 50%. The principle reason for the reduction in braking power is heat build-up within the braking system.
Another problem associated with vehicle braking systems is in the transmission of the heat generated in the braking system to the wheel bearing of the vehicle. Wheel bearings have generally been protected from transfer of heat from the braking system, as the life of the wheel bearing would be substantially reduced if exposed to the heat generated in the braking system. Therefore, the prior practice has been to isolate the wheel bearing from a direct heat transfer path of the braking surface to the wheel bearing.
Other demanding brake applications include airplanes, trains and race cars. The problem of heat build-up is often compounded in commercial brake applications where shields or other protective members are required to avoid dirt or water maintenance problems. These members further reduce the efficiency of heat transfer to the surrounding air.
In braking systems, brake pads are moved to engage the braking surface and are retracted to disengage the brake. Most disc brakes rely on the rotating disc to "kick back" the pads. It is desirable to have the brake pads retracted to a fully clear position to avoid drag and unnecessary brake pad wear. In ring brakes, the brake pads are larger and a higher retraction amount is desired, preferably about 0.030 of an inch. Retraction distance is also tied to brake pedal travel, both of which can be affected by brake pad wear. It is therefore desirable to have a retraction mechanism which provides this retraction distance and corrects for brake pad wear. The ring brake can use relatively large brake pads to increase the contact area whereby brake pressure can be reduced. Furthermore, speciality high temperature, low wear materials used in disc brakes and racing car brakes are avoided.
Considerable forces trying to strip the brake pads from a retainer are encountered in ring and disc brakes and a simple arrangement for countering a portion of the forces would be desirable.
In ring brakes in particular, there remains a need for a simple brake pad structure as well as a simple brake pad actuating arrangement.